Method for the extraction of petroleum by mining operations



Aug, 6, 1940- K. GROSSE ET AL 058 METHOD FOR THE EXTRACTION 0F PETROLEUMBY MINING OPERATIONS Filed Sept. 12, 1938 5 Sheets-Sheet 1 7 Fig.7 3 3 2Q. a l-"f' 7 Kar/ crease. Clint/Lev ScA/a'cfit Attamofs I Aug. 6, 19.40.H GRQSSE AL 2.210582 METHOD FOR THE EXTRACTION 0F PETROLEUM BY MININGOPERATIONS Filed Sept. 12, 1938 5 Sheets-Sheet 2 fnrenforsi v I /fzvrlGrosse "1 cinfh s /llicfit B) iii Wm flttovneys Aug. 6, 1940. K. GROSSEEl AL METHOD FOR THE EXTRACTION OF PETROLEUM BY MINING OPERATIONS 6Sheets-Sheet 4 Filed Sept. 12, 1938 fnvenfar'sx life run a g- 1940- K.GROSSE El AL 2.210.582

METHOD FOR THE EXTRACTION 0F PETROLEUM BY MINING OPERATIONS Filed Sept.12, 1938 6 Sheets-Sheet 5 Aug. 6,' 1940. K. GROSSE ET AL.

METHOD FOR THE EXTRACTION 0F PETROLEUM BY MINING OPERATIONS 6Sheets-Sheet 6 Filed Sept. 12, 1938 Patented Aug. 6, 1940 METHOD FOR THEEXTRACTION OF PETRO- LEUM BY MINING OPERATIONS Karl Grosse and GiintherSchlicht, Wietze, Kreis Celle, Germany, assignors to Deutsche PetroleumAktiengesellschaft, Berlin Schoneberg,

Germany Application September 12, 1938, Serial No. 229,480

. In Germany September 11, 1937 15 Claims.

In view of the fact, that petroleum cannot be extracted completely byboring operations alone and that partly the degree of yield is even anextremely low one, it has already been suggested by various interestedparties to work the petroleum deposit by means of mining methods. Thesuggestions which have become known in this direction principally aim atrendering the deposits accessible by driving drifts above or below thedeposit in order to subsequently tap it and to convey petroleum,escaping from the borings above ground. In connection with the tappingof the deposit by borings measures have further been suggested,according to which the extrac-' tion of the oil or petroleum is to befurthered by forcing in gas, gaseous media or chemicals.

Furthermore, it has also been already suggested, when driving a shaft,to degas the petroleum deposit in the first instance to the furthestpossible extent by borings and subsequently to sink a pit horizontallyin the layer or stratum enclosing the petroleum for the purpose'ofdriving a network of drifts'underneath the deposit and to tap it in theusual manner by borings.

i All these known methods embody the tendency to remain, when recoveringthe petroleum by mining methods, outside the deposit proper and-toapproach the latter merely by tapping operations. But also these knownmethods are fundamentally subject to the drawback, characterising actualboring operations, that the petroleum can never be wholly recovered.

The present invention relates to a method of extracting or recoveringpetroleum, in which all disadvantages of the known methods have beeneliminated and whichcreates for petroleum mining a solution whollymeeting not only all demands which can be made from a technical andsafety point of view, but also renders it possible to recover thepetroleum to such an extent that practically not a drop is left back.The method according to the present invention essentially consiststherein, that the deposit is first degassed to the furthest possibleextent and petroleum partly preliminarily recovered. Subsequently it iscompletely drained by means of. a drift system driven through thedeposit proper until complete stability has been attained, whereuponthe'rock, containingpetroleum, is recovered by immediate miningoperations. In connection with the method according to the presentinvention a drift network is thus driven or sunk in the deposit proper,for the purpose of procuring a drainage system partly removing thepetroleum from the floating deposit and rendering it stable forsubsequent mining operations. The removed oil sand is then dressedorwashed according to a certain dressing method, so that an almostcomplete recovery of the oil, contained in the deposit, is attained.

In connection with the method according to the present invention, allmeasures preceding the driving of the drift network and the extractionof the oil from the deposit proper are aiming, from the very beginning,at the complete recovery of the oil as far as this is possible. Duringthe last-mentioned working phase it is possible to watch the depositimmediately with regard to the progress of the extraction of thepetroleum and to influence this in such a manner, as may be required byvthe finally, following mining operations. In accordance therewith, afurther suggestion of the present invention consists therein, to carrythrough the preliminary recovery of the petroleum through the medium ofthe borings applied from the outside only so far as to render thedriving of drifts within the deposit possible and to continuouslysupervise its progress by means of rock samples, core samples or thelike until the time for tapping the deposit appears to be appropriate.In the method according to the present invention the deposit is thusfirst to be rendered ready for tapping operations. This will essentiallybe attained that by means of preliminary boring operations from aboveground sufflcient borings are pushed into the deposit in order to ensureas extensive a degassing as possible. The recovery of oil simultaneouslycarried-through must not exceed a degree of recovery which is requiredfor carrying through economic mining operations in connection therewith.

According to the suggestion embodied in the present invention, thenumber. of borings providedabove ound is generally smaller than would berequired for the extraction of oil by boring operations alone.Similarly, as far as the prevailing conditions require and render itpossible, the preparation of the deposit can be eifected by upper andunder walls, in connection with which these borings are not to serve thepurpose of entirely draining the deposit of petroleum either, but merelyfor attaining the aim, to render the deposit accessible for immediatepetroleum mining operations, not only from a technical, but also from asafety point of view.

As soon as a deposit, by reason of the aforementioned measures; isconsidered ready for mining operations, the mining operations proper canbe commenced, viz. as drainage of the deposit being, for the time being,yet in a floating state. In connection herewith it must be pointed outparticularly, that the method in accordance with the present inventionfurnishes the possiare retained, in consequence of surface and limitingface tension, by the petroleum carrier, has

not yet been attained. This ensures for petroleum mining a reliableeconomic basis, because, generally speaking, an excessive recovery ofpetroleum from the deposit by boring operations which is still furtherincreased by the known methods, such as repressuring or flooding,extracts, on the one hand, too muchpetro leum from the deposit to ensuresubsequent economic mining operations and, on the other hand, leavesconsiderable residues of petroleum in the deposit which will then befinally lost to economic life and purposes.

In the method according to the present in-. vention, the drainage of thedeposit with the aid of the drift network can be carried through to adegree of recovery by providing the proper number of drifts anddimensioning the drifts, which, on the one hand ensures an economicdressing of the oil sand. In connection herewith the driving of thedrifts'at gallery driving speed and planning of the drift networkaccording to the method embodied in the present invention,-i. e., at thedistance of the running and dipping drives, are so related to each otherthat, on the one hand, a satisfactory degree of recovery is attainedand, on the other hand, the deposit is rendered stable within so short aperiod, that the complete extraction of the oil sand on a large scaleaccording to any desired mining method may be carried out immediately.In accordance with the present invention, for instance, the roofs aredriven prior to the driving of the floors, so that the petroleum isrecovered in a downward direction, whereby unnecessary double measuresare avoided.

In consideration, that the drive of the drifts is effected in floatingrock (quicksand) and partly with complete piling, not only in the roofand at the face, as well as in front of the breast there is, on theother hand, the necessity of providing sufficient filter possibilitiesfor the recovery of petroleum from the sand, without creating apossibility for the latter to subsequently shift. To this end, apartfrom leaving corresponding joints between the timbering, appropriatefilter materials are provided and accommodated between the facing boardsand the deposit, e. g., straw, heather, filter cloths and the like. Indrifts, which for a longer life have been bricklined, filtering materialis also provided behind the brick lining. For the purpose of allowingthe oil to pass through, openings are provided in the brickwork in anappropriate manner, be it by leaving a space betwen the joints or bywalling in pipes. connected in the drift directly to the pipe system,into which the petroleum, accumulating behind the brickwork, is let offfrom time to time. In this way a contamination of the sole through thepetroleum will be avoided. It is a matter of course, that at this pointalso the tapping of the deposit by means of filter boreholes in the mostdifierent directions has to be considered. It is, furthermore,necessary, to provide in the sole a sufficient number of filter wellswhich, apart from the extracting of petroleum from the oil sand belowthe sole, serve the purpose to collect the petroleum oozing into thedrift, subsequently being fed to the wells by-appropriate appliances, e.g., channels, nomatter what material they are made from.

In this-and a similar manner, the drainage is regulated by increasingorreducing the filter:

When walling in pipes, the latter are ing process ad lib., in themethodaccording to the present invention. 1

According to a further suggestion embodied in the present invention, thedegree of petroleum extraction can be eifectively regulated by settingthe filtering process or the drainage of the entire drift system or partsections thereof under pressure or under-pressure. In consequencethereof, a further increase of the extraction of petroleum can beadvantageously attained, by setting the drift system or its sectionscontinuously or intermittently under an underpressure, with the aid ofthe ventilation. In

' connection herewith, the continuous or intermit tent under-pressurecan be produced either by means of ventilators, as for instance, byincreasing the eficiency of the main ventilator beyond the extentactually required for ventilating purposes, special ventilations or bythrottling the standard air current. The latter, particularly, can berealized in such a manner, that at the proper times the introductoryshaft is covered up, whilst the ventilator is allowed to suck. In partfields of the workings, the depression increase can be attained eitherby suitably tightening up the ventilation channels and connecting thelatter to boreholes or by creating in suitable drifts, which have beenparticularly carefully tightened, a vacuum, which causes petroleum to beextracted from separate workings. All these measures are alsopermanently carried through whilst having in view the aim proper of thepresent invention, viz. the stabilization of the deposit for the purposeof mining.

It goes without saying that in connection with the method according tothe present invention also the measures known per se, according to whichWater, steam or air is forced into the deposit, or an addition ofchemicals is effected, which destroy the surface tension of thepetroleum adhering to the grains of sand or work as displacement medium,can be employed.

The petroleum, collecting in the drifts, is automatically forced into apipe system extending throughout the working and that by means ofpressure apparatus which, after the float principle, either works bycompressed air, steam or also electricity or are built-in in the oilsumps along the sole. perienced a further preferred development, byaccommodating draining pipes in provisionally driven drifts for catchingthe petroleum oozing out, which do not require to be kept opensubsequently. As soon as the working condition of these draining pipesrequires it, they may be cleaned at regular or irregular intervals bymeans of steam, water, air or gaseous media or, finally, by any desiredmechanical means. In accordance with the suggestion embodied in thepresent invention it will further be possible to use these drainingpipes for pressure or depression methods.

The quantity of petroleum extracted will then be constantly controlledby installing suitable measuring appliances. The aforementioned methodis important for reasons of safety in so far as it renders permanentworking in the drifts provided for the recovery of petroleumunnecessary, except when repairing work has to be carried out.

As soon as the deposit has been stabilized, so that it can be said to beready for mining operations, which in turn has to be ascertained in asuitable manner by constant examinations of The present invention alsoexthe petroleum carrier in order, as already previ- 75 ouslymentioned,not to carry the petroleum extraction too far so that there would be arisk of the mining operations becoming uneconomical, the latter can beprepared for and carried through in accordance with appropriate methods.

In consideration of the fact, that mining operations are to be preparedand carried out at'that moment at which the required stability has justbeen attained, the petroleum carrier is extracted according to specialmethods. In connection herewith it should be borne in mind that thedegree of stability attained with the aid of the aforementioned measuresis not, what can be called, a considerable one, nor that it can be avery considerable one, as it usually is in other branches of mining. Inconsequence thereof, the extraction must take place secured by piling,whereby in specially developed methods auxiliary working and mainworking is utilized and the place is created for the placing of the workwhilst driving the roofs and leaving a special rock-staple for each noglength.

Leaving a rock-staple will ensure that the deposit, still in the lowerlimits of its stability, will not reach the breast or front but be helduntil the completion of the timbering or lining. A special peculiarityof the extraction of the petroleum deposit, which is incontradistinction to methods developed in other branches of mining isthat the pressure wave is so regulated, that it rests on the stowing andnot on the breast or front. Also in this instance, that the working iscarried through similarly to the driving of drifts, that it progressesfrom the top to the floor and the hanging pillar of a set of working isworked, as far as possible, previouslyto the floor.-

In the method according to the present invention the worked hollowspaces are, furthermore preferably walled again, for which purpose thewashed petroleum sand should be used as far as possible as coggingmaterial. For this purpose the washed out petroleum sand is suitablymixed. with an appropriate loosening material, as, e. g., saw-dust, slagor the like, in order to reduce its degree of moisture, particularly, ifclay is contained therein, and so to reduce its tendency to cake. Theintroduction of the gobbing from above ground into the undergroundworkings is best effected in a dry form, viz. through suitableboreholes, which were systematically provided previously for thatpurpose at the time of rendering the deposit ready for mining purposes,so that, according to the condition of working a suitable borehole wasavailable or, if necessary, could easily be newly provided, if required.From the gobbing sole to be considered, the gobbing material is taken inan appropriate manner, as far as possible by using shutes to the gobbingpoint proper. In connection herewith it has been ascertained, that theextraordinarily strong sog,

. produced by the dropping of the gobbing material, can be utilised forventilating purposes not only in the gobbing borehole, but also in theshutes. This mode of working can, f. i., be used for. phase-wise orsudden exhaustion of bad intakes in front of dead faces and corresponds,

.as a whole, to the principle of the water-jet pump.

Furthermore, the gobbing boreholes can be used not only for conveyingthe gobbing material into the underground working, but also'for theconveyance of the lining material, e. g., props, caps and laths. Theseare thrown from above ground down a depth of several m. In order toprevent the material thus thrown down, from being damaged, suitable sandbolsters or such made from peeled off bork, should be used. Thisv methodhas, furthermore, been developed in such a manner that, for the purposeof retarding the velocity of fall, especially in connection withconsiderable depths, the borehole is immediately covered up after theobjects in question have been dropped in. 1

The petroleum sand obtained in the drifts or when working is conveyed tothe pit eye and thence above ground. The conveyance to the pit eye iseffected according to the usual methods using, as far as possible,shutes for that purpose which are provided with suitable trap bridges orcascade grates which simultaneously ensures a disintegration of thelarger pieces. In this connection the belt conveyor has been adoptedagain in the first instance, because this embodies the advantage ofallowing the-drifts to converge to the smallest possible cross section,in connection, with which material or persons can be conveyed by meansof these belts. The employment of rubher belts stands in the foreground,the risk of decomposition in this case being met by providing the rubberbelt with a coating of moist sand, gobbing sand or sand with aninconsiderable percentage or content of petroleum.

Further advantageous examples of performance of the present inventioncan be gathered from the drawings in which the invention is elucidatedwith the aid of a few examples of performance. g

Figs. 1 and 2 show the initial steps for mining a petroleum depositaccording to the present invention in schematic representation incrosssectional and plan view.

Figs. 3 and 4 show the driving of drifts in quicksand and Fig. 5 in dryrock,

Fig. 6 is a graphic representation for elucidating the suitable speed indriving drifts, whilst Fig. 7 illustrates a schematic plan view of apart of a. set of workings.

Figs. 8 and 9 show a working in plan and crosssection and a Fig. 10 afurther schematic representation of a set of working, whilst Figs, 11and 12 represent an example of performance of a conveyor device foroozed oil.

7 According to Figs. 1 and 2 the petroleum deposit is, in the firstinstance, preliminarily extracted through borings 2 from above ground,in connection with which less boreholes are sunk than is usual with theordinary boring methods. After terminating the preliminary petroleumextraction operation through the boreholes 2 or simultaneously with it,the deposit is explored by means of a shaft 3 being sunk, as far as thisis possible, in petroleum-free partition rock, and by .cross cuts 4, aswell as by floors and tops 5.

Where working conditions render it necessary, the deposit can further beopened up partly byworking under an edit, e. g., above a blind shaft 6.Proceeding from the drifts 5, the deposit is preliminarily exploited bymeans of horizontal and sloping borings I up to a degree which ren- 55dersit possible, that now the drive of drifts can be effected within thedeposit proper. According to the prevailing conditions, which may varyvery considerably with the fine or coarse grain or with the firmness ofthe petroleum-containing layers, the horizontal or sloping borings canalso be dispensed with for further preliminary deoiling, in order toimmediately start with driving drifts within the deposit proper. If thepre-- liminary extracting operations through the mev76 dium ofabove-ground'borings or by means of horizontal and sloping borings havenot proceeded further and that the rock is still in a floating state,the drive of drifts according to Figs. 3 and 4 is to be effected. Thefaces, the sole or floor and the roof and even the fore-heads are, inconnection therewith, sustained by piling, the joints of the separatelaths are tightened by filtering material as, e. g., straw, heather orthe like, in order to retain the rock whilst allowing the petroleum topass through. The petroleum escaping into the drift is collected in thechannels 9 and fed from there or immediately to the filter well I 0,arranged at a distance, in which the pressure apparatus H are located.The latter are, e. g., actuated by compressed air, taken from an airconduit l2 and work in accordance with the principle of the steam traps,periodically forcing the oil, which has meanwhile collected, into apetroleum pipe l3. The kind of petroleum conveyance just referred topossesses, relatively to the conveyance by pumps or other means, quiteextraordinary advantages.

According to the present invention, the preliminary extraction ofpetroleum and, if necessary, the drive of drifts is to be carriedthrough in such a manner that the rock at the head end is no longer in afloating state but already rendered stable to such an extent, that alining or timbering of the drift drive is effected in the manner, asshown in Fig. 5 representing dry rock, where instead of the head lininga rock pillar I4 is left standing in the first instance until theauxiliary as well as the main working is finished. The manner, in whichthis state of stability in dependence upon the petroleum deposit of therock is to be attained, has been illustrated schematically in thegraphic representation according to Fig. 6.

In the representation according to Fig. 6 the petroleum content has beenrepresented on the abscissa including" water in weight-percents, whilston the ordinatethe driving efliciency per layer has been plotted. Therepresentation allows of recognizing without any difficulty whatsoeverthat the driving efficiency being found rises, in the first instancewith decreasing petroleum content up to a maximum; this most favorabledriving efliciency at about 15 to 10% oil or petroleum content. If thepetroleum content is still further decreased below this limit, thedrivingefiiciency also drops again considerably, because then theextraction possibility of the rock will become less favorable. Accordingto the suggestion embodied-in the present invention, the preliminaryextraction and the drift drive must be so adjusted, that the depositexhibits the most favorable moisture content situated, by way ofexample, between 15 and 10%, at which the stability possesses itsoptimum Within the meaning of the present invention. It goes withoutsaying, that the limits of 15% or 10% are not to' be understood to beabsolute, because these may vary considerably according to the nature ofthe deposit. Thus, a finely grained sand is stable already at a greatercontent of petroleum, whilst with a coarsely grained sand thepreliminary extraction must be carried on further to attain the samestability. The accurate limits thus depend upon the working conditionsprevailing at the time and in connection herewith it is important, thatalso the preliminary extraction through the medium of the drift systemfor the preparation for the mining operations is carried through to suchextent,

drifts 24 in separate sets that also for the immediate exploitation ofthe deposit even by mining operations this most .favorable stability isattained, at which the floating condition of the rock is not attained orreached by a narrow margin.

In Fig. 7 the petroleum deposit has again been characterized by thereference numeral I, the shaft by the numeral 3 and the cross-cut.exploration by the numeral 4. The set of workings proper is sub-dividedby the drainage drifts l5 into separate sections, the interdistance ofwhich depends upon Working conditions and is so chosen, that the maximumstability, illustrated in Fig. 6 is attained for mining purposes.Subsequently, the mining operations proper are carried out according tosuitable methods, as shown at l6 by way of example. The numeral llcharacterizes a borehole, through which gobbing and other material isconveyed from over-ground. In the represented example of performance asseen in Fig. 7 the winning is effected from above progressively, becausein the example of performance, on which the representation has beenbased, the necessary condition for mining has already been attained inthis part of' the deposit by drainage. It certainly goes without sayingthat working conditions can well be imagined, at which mining is takenin hand at first in'the. lower part of the deposit.

As can be gathered from Figs. 8 and 9, the mode of working isessentially identical with a breast-wall usual in pit coal mining. Itconsists of the set of workings IS, the hurrying panel l9 and thegobbing panel 20. The conveyance in the hurrying panel is suitablyefiected by means of the conveyor belt 2i, whilst in the panel 20 thegobbing material is advantageously conveyed by means of a shaking trough22. The face of workings is taken in hand in a manner similar to thatshown in Fig. 3, so that between the separate working sections in thefirst instance pillars 23 are left standing -in front of the face of theworkings, until the complete lining which,

in the roof, is efiected by timbering, has been placed in position. Onlythen will the pillars 23 be removed, as well, if this should benecessary, a panelling of the face of the working, whatever may berequired by working conditions. In

connection herewith it is of extraordinary importance to so carry on themining operations in regard to rapidity of the working and theintroduction of the gobbing, that the pressure wave is made to rest onthe gobbing panel 20 and the actual set of workings I8 is released.

According to Fig. 10, the petroleum deposit is subdivided by the maindrift 25 and the running of working 25. The running length of the set ofworkings is, according to the present invention, to be dimensioned at150 to 250 m., whilst the fiat working height amounts to about 50 to m.,depending, with regard to its dimensioning, upon the condition of thedeposit. In the represented example of performance it has been assumed,that in the working 25 mining operations have already started. Underthis supposition the drift 24a and the drift 124b, shown in therepresented example of performance, have been closed up by the dam 26,in connection with which the drift 24a is set under over-pressure, forthe purpose of forcing the petroleum, still contained in the Workingsection, into the drift 240 located under neath. The oozing drift 24b,however, is set under under-pressure for the purpose of accelerating theextraction of petroleum in the adjoining working sections. The numeralI3 is again made to characterize the oil pipings and II the separatefilter-wells or pressure apparatus.

In the device for conveying oozed petroleum, shown in Figs. 11 and 12 byway of example, resembling a pressure apparatus, the petroleumcollecting piping has also been characterized by the numeral l3 and thepressure piping which is fed with compressed air, by the numeral l2. The

.oozed petroleum is fed through the piping 28 with return valve 29 tothe housing 21. The petroleum level, rising in the housing 2'! actuatedthereby in an upward direction a float 30 attached to a rod, until thefloat, by means of suitable devices, which can be gathered from thedrawings, opens in its highest position the inlet valve of thecompressed air piping l2. The compressed air, subsequently penetratinginto the housing 21 effects the conveyance of the petroleum which hasmeanwhile collected in the housing 21 into the oil piping I3, inconnection with which the returnvalve 29 is closed owing to theincrease.

in pressure. Between the float 30 or its guide rod and the inlet valvefor the compressed air, appropriate elements, for instance, in form of asling-belt, have been arranged with the result that the float opens orcloses only when in its uppermost or lowermost position. In connectionherewith the arrangement has been made, that the float in its lowermostposition simultaneously also opens the ventilation valve.

The essence of the present invention is, however, in no way confined tothe represented examples of performance, it is rather possible to effectthe realization in any other desired manner according to the prevailingmining and working conditions. Essential is for the sense of the presentinvention, that all measures serving mining operations are so arrangedfrom the very beginning, that a stability of the deposit is attained,which allows of immediately winning petroleumcontaining rock.

It should, finally, be pointed out, that the conveyance of the recoveredoozed petroleum, as suggested according to the present invention, withthe aid of pressure apparatus actuated by com pressed air, can also beused with advantage in all such cases, where as complete a mining of thepetroleum-containing rock is not the final aim of exploring the depositby means of mining methods, but rather the extraction of the petroleumby means of the drainage system. This suggestion embodied in the presentinvention thus possesses for itself independent importance independentof the total method on which the present invention has been based.

What we claim is:

1. A method for obtaining petroleum from an oil sand deposit whichcomprises drilling into said deposit a number of borings, degasing saiddeposit through said borings, removing oil through said borings untilthe condition of the deposit permits the sinking of a drift networksystem into said deposit, sinking said drift network system, draining byvarying the pressure in the drifts of said drift network system of saiddeposit until the oil sand has attained a consistency permitting it tobe mined, and recovering the oil sand proper by mining operations.

2. A method of the kind described in claim 1 in which the preparation ofthe oil sand into a suitable state for mining comprises placingaltercomprises the steps of driving the sloping drifts and then drivingthe horizontal drifts.

4. A method of the kind described in claim 1 in which the recovery ofthe oil sand by mining operations includes the step of exploiting thedeposit from the roof to the floor of the working.

5. A method of the kind described in claim 1 in which the recovery ofthe oil sand b-y mining operations includes the step of introducing intothe exploited deposit a mixture of sand from which the oil has beenextracted and a loosening material such as sawdust, slag or the like.

6. A method of the kind described in claim 1 in which the recovery ofthe oil sand by mining operations includes the step of tamping the oldworkings with cleaned oil sand.

7. A method of the kind described in claim 1 in which the recovery ofthe oil sand by mining operations includes the step of regulating thepressure wave so that said pressure wave lies in the cogging field.

8. A method of the kind described in claim 1 in which the recovery ofthe oil sand by mining operations includes the step of exploiting thedeposit of oil sand in such relationship to the tamping of the exploiteddeposit that the pressure wave rests in the cogging field.

9. A method of the kind described in claim 1 in which the recovery ofthe oil sand by mining operations includes the step of tamping the oldworkings with a filling material.

10. A method for obtaining petroleum from an oil sand deposit whichcomprises drilling into said deposit a number of borings, degasing saiddeposit through said borings, removing oil through said borings untilthe condition of the deposit permits the sinking of a drift networksystem into said deposit, sinking said drift network system, drainingsaid deposit until the oil sand has attained a consistency permitting itto be mined, and recovering the oilsand proper by mining operations.

11. A method of the kind described in claim 10 in which the sinking ofthe drift network system comprises the steps of driving the slopingdrifts and then driving the horizontal drifts.

. 12. A method of the kind described in claim 10 in which the recoveryof the oil sand by mining operations includes the step of exploiting thedeposit from the roof to the floor of the working.

13. A method of the kind described in claim 10 in which the recovery ofthe oil sand by mining operations includes the step of introducing intothe exploited deposit a mixture of sand from which the oil has beenextracted and a loosening material such as sawdust, slag, or the like.

14. A method of the kind described in claim 10 i in which the recoveryof the oil sand by mining operations includes the step of tamping theold workings with cleaned oil sand.

15. A method of the kind described in claim 10 in which the recovery ofthe oil sand by mining operations includes the step of tamping the oldworkings with a filling material.

KARL GROSSE. GUNTER SCHLICHT.

